Lapping: Occurs where wet and dry layers overlap during painting. Avoid with paint area management and technique.
Lapping probable causes: Wet and dry layers overlapping. Too much heat or wind during application. Inadequate stirring and improper thinning. Extremely porous surface. Painting too large an area at one time, such as trying to go from the top to the bottom.
Lapping solutions: Another coat of paint evenly spread usually will cover lap marks. If the finish coat is relatively transparent or if the surface is overly porous, a primer or second coat may be necessary. Always paint from wet to dry and in small sections to keep a wet edge.
Primers & exterior finishes: Extremely porous painted or unpainted surfaces need a primer/sealer coat before a new top coat. Select a top quality finish in the color and sheen of your choice.